I just found out my posts are finally going through without any changes using the nginx proxy container to nginx ingress method! If you do have a way to do it all directly through nginx I'd love to see how it's all done, maybe I was missing something outside of the snippet you posted.
Since it's currently working I'll look into spinning a test instance up when I get a chance and play with that ingress annotation.
Yeah the separate nginx container just feels... Hacky lol